Ore reduction apparatus



Sept. 18, 1945. E. M. WANAMAKER ErAL ORE REDUCTION APPARATUS Filed April 19, 1944 3 Sheets-Sheet l @maw ff l

Sept. 1945. y E. M. WANAMAKER ETALY 2,384,852

ORE REDUCTION APPARATUS Filed April 19, 1944 3 Sheets-Sheet 2 sept. 18, 1945.

E. M. WANAMAKER ETAL ORE REDUCTION APPARATUS Filed April 19, 1944 3 Sheets-Sheet Patented Sept. 18, 1945 oaE REDUCTION APPARATUS Elmer M. Wanamaker, Knoxville, Tenn., Robert H. Cromwell, East Orange, N. J., and Harold L. Chamberlain, Knoxville, Tenn., assignors to Electro Manganese Corporation, Tenn., a corporation of Delaware Knoxville,

Original application August 4, 1943, Serial No. 497,352. Divided and this application April 19, 1944, Serial No. 532,020

(Cl. 26S-18) 15 Claims.

This invention relates to apparatus for effecting a thermal reduction of ores, particularly ores containing higher oxides of manganese, in order to reduce these higher oxides to a form readily soluble in acids and is a division of our copending application Ser. No. 497,352 filed August 4, 1943. In the electrowinning of manganese from its ores it is necessary iirst to convert the manganese in the ore into a soluble salt thereof, as for example by leaching with a mineral acid, sulphuric acid being commonly employed for this purpose. A high manganese vextraction eliiciency is a vital factor in the commercial success' of the process.

'In some manganese ores the manganese naturally occurs in a form readily leachabletherefrom by means of mineral acids, but in other ores, particularly those containing higher oxides of manganese, the latter is not efficiently extractable by direct treatment of the ore with the acid, and with such ores the problem of devising appartaus and process for conditioning the ore to render it eiilciently extractable with acids has arisen.

One of the objects of the invention is the solution of that problem.

The principles of the invention as to process and apparatus will be defined in the appended claims and illustrated in the following description and drawings, in which:

Fig. 1 is a vertical section on the line I-I of Fig, 2;

Fig. 2 is a view partly in section on the line 2-2 of Fig. 3; A

Fig. 3 is an elevational view partly in section on the line 3-3 of Fig. l;

Fig. 4 is a sectional elevation on the line 4-4 of Fig. l; l

Fig. 5 is a section on the line 5-5 of Fig. 1;

Fig. 6 is a sectional viewon the line 6--6 of Fig. '7; v

Fig. '7 is a section on the line `I`I of Fig. 6;

Fig. 8 is a fragmentary side elevation of one of the heating conduits and associated apparatus;

Fig. 9 is an end View partly in section on the line 9-9 of Fig. 8; and

Fig. 10 is a fragmentary perspective end view of two companion heating units and associated apparatus.

In the drawings a pair of heating conduits is shown. It will be necessary to describe only one in detail since the members of the pair are identical in structure. 'Ihe conduit I shown in the drawings has a total length from end to end of about feet and a diameter 'of about 1 foot and f brackets 5 carried by suitable supporting structure including the table 1 having legs 8 carried on and supported by a pair of I-beams 9, the rollers 4 engaging bearing rings I'I welded to the conduit I. At least one of the rings, IIA, is grooved and engages a bevelled roller 4A. These I-beams run the entire length of the apparatus as shown and are connected together and braced by cross members I2. The support comprising'the I-beams 9 and cross members I2 rests pivotally at one end on a shoe I4 and at the other end on an adjustable jack I5 so that the supporting structure and conduit resting thereon may be given an adjustable inclination to the horizontal. Intermediate the ends of each of the conduits I and 2 there is provided an annular sprocket collar I1 driven by diagrammatically indicated sprocket chains I8 from the sprocket wheels I9 (only one of which is shown) which in turn are driven by the sprocket wheels 20 mounted on the shaft 22 journaled in the bearings 23, the said shaft 22 forming a partof a driving mechanism including the motor 24 and the speed reduction mechanism indicated generally as 25. The motor 24 and associated driving mechanism is supported on a platform 29 secured to the I-beams. At one end of the pair of heating conduits I and 2 there is provided means for feeding into each conduit a mixture of pulverized ore, e. g., manganese ore containing higher oxides of manganese and iinely vdivided carbon. This comprises a screw conveyor (including the helical plates 32 carried on a shaft 33) and mounted partly within a conduit 3l, one end of which conveyor terminates in a hopper 34 and the other end of which extends into the heating conduit and is open for the delivery of the mixture of ore and carbon into that heating conduit. A bracket carried by the screw conveyor at one end carries a bearing 38 in which the shaft 33 is mounted at the delivery end of the screw conveyor, the other end of the shaft 33 extending through the wall of the screw conveyor and carry.- ing a sprocket wheel 39 which is driven by sprocket chain 40 from the sprocket wheel 4I carried on a shaft 42 journaled in a bearing 43 and driven by a motor 44 through speed reduction mechbolts, a collar 5l having a hole in the center thereof. 'I'he inside annularedges deiining this hole are in spaced relation to the cylindrical wall 8| of the screw conveyor so that between that wall of said' conveyor and the said annular edges of the hole in the collar there exists an annular space 55. The radial dimensions of this space may be controlled by providing collars having holes of varying diameters. The purpose of this annular space 'and the control of the size thereof 'lis to provide adjustable orifice means to restrict the iiow of gas from the inside to the outside of the heating conduit, to develop super-atmospheric pressure within the heating conduit and to cause a ow of gas from the inside to the outside of said conduit and will be further described.

Means are providedl to :vent gases produced within the heating conduit through this annular space 55 land to remove the vented gases and solidy particlescarried thereby through hoods 56 into a dust separator, e. g., the cyclone separator 51. (Note Figs. 8, 9 and 10.) The structure of the hoods is shown in Figs. 1, 2, 3, 6, 7, 8, 9 and 10. Each of the hood members has substantially vertical outer and inner walls 60 with semi-circular cut-out portions 6| corresponding to the curva-v ture of the Wall- 3| `of the screw conveyor. These walls are connected by lateral walls forming pipes which terminate in a common pipe 64 leading to the intake of a blower 05 driven by a motor 66. The blower discharges through a pipe 61 into the cyclone separator 51 'from which the gas passes through the pipe 68 to a source of disposal. The two hoods 56are fitted over the screw conveyor f 3|, the outside walls of the hoods being in contact with the conveyor and the inside walls of the hoods being spaced from said conveyor (note Fig. 7) to form a semi-annular space 1| corresponding `to the annular space 55 between the screw conveyor and the collar 50 secured to the heating conduit. The inside walls of the hoods are positioned as close to the collars 50 as is possible, just enough clearance being provided to permit rotation of the conduit (note Figs. 7

and 8).

The discharge end of each heating conduit extends into a substantially gas-tight receptacle 14 through circular holes 15 therein and a flexible annular bushing 16 (note Fig. 1) is provided between the wall of the heating conduit and the edges of the holes 15 in order to maintain the gas seal. This bushing may be made of any suitable ilexible gas-sealing material, as for example felt. The lower portion of the receptacle is restricted to form a conduit 11 which delivers the conditioned ore to a screw conveyor 18, the shaft 19 of which is journaled at one end in the bearing 80 and'driven by a sprocket wheel 8|. This sprocket Wheel 8| is driven by any suitable means not specically shown.

The conduit 11 of the receptacle is provided with self-operating valveslin the nature of butterfly valves or swing gates 95. 'Ihese are pro-s vided with counterweights 80 and automatically open and deliver ore when a predetermined Weight of ore suiiicientto dump the valves is delivered thereto. These valves assist in maintaining the receptacle in a substantially gas-tight condition.

Adjacent the feed end of the heating conduit and extending toward the discharge end for a 'length of about 15 feet, is a heating unit 90 which surrounds and heats the pair of heating conduits and provides a hot zone 9d; This heating unit 90 may be, as shown, a substantially rectangular box having steel walls 9| and a number of' lateral. bralng members 92 carried at the botnected by leads 99 to a source of electrical heating current through pyrometer control boxes 99 which automatically maintain the magnitude of current delivered to each group and therefore the heat energy delivered thereto and the temperature developed thereby.

Adjacent the delivery end of the heating conduit and extending for a distance of about 15 feet, there is provided a cooling zone |02 as 'shown in' the drawings (note Figs. 1, 2 and 5). This zone is provided by spray pipes |03 (note Fig.- 5) from which water is sprayed on the surfaces of the heating conduits. The waterso sprayed is received in a trough |00 supported beneath the conduits on brackets |05 which in turn are secured to the legs 0 of the supporting 49 to hopper 34 and screw conveyor 3|.

ganese ore and finely divided carbon is obtained in substantially dry condition, e. g., by feeding dry ore and dry carbon from the bins 38 and While finely divided carbon in general may be used, it is preferred to employ the carbon in a form as pure as possible, as for example powdered charcoal or coke, and it is preferred to employ vat least about 0.9 or on'e atomic weight of carbon for each atomic weight of manganese in the ore, the purpose being to employ an excess of carbon over that theoretically necessary to reduce the higher oxides inthe ore to the manganous condition. The dry mixture is then passed. as a confined stream in a substantially horizontal path through a heated zone of an externally heated conduit, e. g.,A from screw conveyor 3| through hot zone 910.v The temperature of the heated zone is maintained (e. g., by heating units 95,'- 96, 91) sufiiciently high to etect a reduction of the higher oxides of manganese to the manganouscondition, and the time of exposure of the mixture of ore and carbon is controlled so as to render at least about percent of the manganese in the ore soluble in dilute sulphuric acid. In other words, the criterion for controlling the time of exposure of the ore to said high temperature is theextraction eiciency of the manganese in the reduced ore, and this extraction eiliciency should be at least about 95 percent.

In a typical case the temperature developed by the heating units 95, 9S, 91 (which is approximately the temperature within the heating conduit) is about 900 C. It is preferably at least about this temperature and may vary within a range of, for example, about 850 C. to about 1050 C. In the apparatus shown the time of exposure of the ore to .a given high temperature f (the length of the heating zon'e 94 and the dlinear foot per minute.

4ameter of each heating conduit being iixed) will be a function of the ratefoff feed oi' the mixture -of ore and carbon, the longitudinal inclination of the heating conduit and speed of rotation thereof. In a typical case and employing the apparatus above described, these variables may be stated as about '750 pounds per hour of ore plus 10% by weight of reducing agent, an inclination of the` heating conduit to the horizontal of about one inch in three longitudinal' feet, and a speed of rotation of the heating conduit of 3 to 6 R. P. M. The resulting time of exposure of the mixture of carbon and ore in the hot zone 94 is about l minutes and since the length of that zone is about 13 feet, the velocity of forward movement of said mixture is of the order of 1 It will be understood that the step of passing the substantially dry mixture of ore and carbon as a confined stream in a substantially horizontal path through a d heated zone at a predetermined high temperature and controlling the time of exposure to obtain an extraction efciency of at least about 95 per cent of the manganese in theore, is not llmited to the use of a longitudinally inclined rotating conduit but may also be effected by other specific apparatus means, as for example a horizontal conduit with a screw conveyor extending therethrough. ,f I As the mixture passes through the hot zone Sit, reaction of the carbon with the ore produces a gas containing -both carbon monoxide and carbon dioxide and it is desired to exclude air. The preferred manner of excluding air is to generate the said gas at a rate sufficient to maintain it within said conduit at super-atmospheric pressure, vent it through controlled orice means and thus cause `a controlled ilow of gas from the inside to the outside of said heating conduit. The mixture may be fed -to the conduit at a rate which will generate gas at a rate sumcient to maintain it within the conduit at super-atmospheric pressure. The gas thus produced `will be vented through the annular space or orice 55 between the screw conveyor 3l and the collar 5d and thence into the pipe 64. The rate of feed may be correlated with the size of the annular orice to cause the development of a predetermined superatmospheric pressure and a restricted ow of gas from the heating conduits into the hoods 56. In a typical caes and at a rate of feed of about '750 pounds per hour of mixture to be reduced, the radial length of the annular orifice between the screw conveyor 3l and the collar 54 is about three-quarters to one and one-half inches. Under these conditions the gas pressure Within the conduit may rbe of the order of 1/ to 4 inches of water. To secure a higher pressure the size of the orifice may be reduced and/or the rate of feed of the 'mixture of ore and carbon increased. It will of course be understood that various orice means other than that specifically illustrated may be employed. The super-atmospheric pressure developed by correlating the rate of feed with the dimensions of the orifice not only excludes air Ibut also tends to speed up the reaction of the reducing atmosphere on the ore. It will also .be noted that the gas passes countercurrent to the advancing ore and that in the specific illustration described the mixture of ore and carbon is continuously agitated with the gas as it passes toward the feed end counter-current tothe mixture advancing toward the discharge end of the conduit. l

Typical gas analyses of the gas generated within the conduit under 'the above mentioned conditions show from about 23 to about 29 percent carbon monoxide and 48 to 52 per cent carbon dioxide and the balance substantially all nitrogen and inert gases., 'I'he gas is substantially free from water vapor, hydrogen and hydrocarbonsv in free or chemically combined condition. The ,Y

gas preferably contains a minimum of l0 to 20 percent carbon monoxide and a ratio of carbon tdiolxide to monoxide of not more than about 2 The development of super-atmospheric pressure causing a i'low of gas from the inside of the conduit to the outside, is a practical and elcient means of excluding air from the interior of the .heating conduits, and that is its primary purpose.

Since, however, other means of excluding air may be employed,` the process of the invention is not generically limited to the specific air-exclusion step herein disclosed and the apparatus elements for effecting that step.

As the mixture passes through the heating con-l duit itis preferably continuously agitated with the said gas in both the hot and cool zones S4 and I 02. Inthe specific apparatus shown this agitation may be effected at least in part bythe continuous tumbling `of the mixture by the rotation of the heating conduits I and 2. Rabbling may also be employed to assist in the agitation, as for example by means of a rabbling tool inserted through the annular space 55 between the screw conveyor and the collar. It will be understood that the inclined conduit shown in the drawings is regarded as substantially horizontal for the purpose of the method of the invention. It will be possible to eilect the agitation in a strictly horizontal conduit by various means which will be clear to those skilled in the art, in the light of the present disclosures.

After the mixture has passed the hot zone 94. it then passes into the cool zone |02 and is there cooled in contact with the gas generated in the hot zone. In the cool zone the mixture may be cooled to approximately room temperature. From the -cool zone the mixture discharges into the receptacle 14 and then passes out of the apparatus Via the screw conveyor. The said receptacle 'I4 is of course also charged with the gas .generated in the hot zone so that the reduced ore may be maintained in contact with the gas until it leaves the apparatus and is sent to a place of disposal, as for example a station for extraction.

We claim:

1. Apparatus adapted for the reduction of manganese ores with carbon comprising an elongated heating conduit having a substantially horizontal straight line axis, a feed end and a discharge end; said feed end having orifice means providing a restricted flow of gas from the inside to the outside of said conduit; means at'the feed end, adapted to feed a mixture of ore and carbon into said heating conduit; means to advance said ore through said conduit from the feed end to the discharge end; means to maintain a predetermined portion of said conduit extending from the feed end toward the discharge end at a predetermined temperature; means to cool a predetermined portion of said conduit extending from the discharge end toward the portion provided with heating means; a receptacle, connected to the discharge end of the conduit, to receive reduced ore; means to maintain said discharge md and receptacle in a substantially gas-tight condition; and means at the feed end of said conduit to receive gas generated in said conduit 'and vented through said orice means.

2. Apparatus adapted for the reduction of manganese ores with carbon comprising an elongated cylindrical heating conduit having a substantially horizontal straight line axis, a feed end and a discharge end, said feed end having orince means providing a restricted flow of gas from the inside to the outside of said conduit; means at the feed end, adapted to feed a mixture of ore and carbon into said heating conduit; means to advance said mixture through said conduit from the feed end to the discharge end and to agitate said mixture as it advances; meansto maintain a predetermined portion of said conduit'extending from the feed end toward the dischargeend at a predetermined temperature; means to cool a predetermined portion of said conduit 'extending from the discharge end toward the portion provided with heating means; a receptacle, connected to the discharge end of the conduit, to receive reduced ore; means to maintain said discharge end and receptacle in a substantially gas-tight con-y dition; and means at the feed end of said conduit to receive gas generated in said conduit and vented through said orifice means.

3. Apparatus adapted for the reduction of manganese ores with carbon comprising an elongated cylindrical heating conduit having a straight line axis slightly inclined to a horizontal plane, a feed end and a discharge end and being mounted to rotate about said axis, said conduit being open at both the feed end and discharge end and having interior surfaces defining an empty space providing for the free and unobstructed passage of solid material therethrough; said feed end having orifice means providing a restricted ow of gas from the inside to the outside of said conduit; conveyor means at the feed end, adapted to feed a mixture of ore and carbon into said heating conduit; means to rotate said conduit to advance said ore through said conduit from the feed end to the discharge end and to agitate the mixture as it advances; means to maintain a predetermined portion of said conduit extending from the feed end toward the discharge end at a predetermined temperature; means to cool a predetermined portion of said conduit extending from the discharge -end toward the portion provided with heating means; a receptacle, connected to the discharge end of the conduit, t0 receive reduced ore; means to maintain said discharge end and receptacle in a substantially gas-tight condition; and means at the feed end of said conduit to receive gas generated in said conduit and vented through said orifice means.

4. Apparatus adapted for the reduction of manganese ores with carbon comprising an elongated cylindrical heating conduit having a straight line axis inclined t0 a horizontal plane, a feed end and a discharge end, said feed end having edge portions defining a circular opening; conveyor means at the feed end, adapted to feed a mixture of carbon and ore into said heating conduit, said conveyor means having cylindrical walls extending into the space within said conduit and defining, with said edge portions, a restricted annular opening of predetermined dimensions:

. vassesses means to rotate said conduit about its said axis and thereby advance said mixture through said conduit from the feed end to the discharge end at a predetermined rate; means to maintain a predetermined portion of said conduit Aextending from the feed end toward the discharge end at a predetermined temperature; means te cool a predetermined portion of said conduit extending from the hai-ge end toward Ithe portion provided with heating means; a receptacle, connected to the discharge end of the conduit, to receive reduced ore; means to maintain said' discharge end and receptacle in a substantially gastight condition; and means at the feed end of said conduit to receive gas generated in said conduit and vented through said restricted opening.

5. Apparatus adapted for the reduction of ores comprising an elongated heating conduit having a Asubstantially horizontal straight line axis, a feed end and an open discharge end; said feed end having orifice means providing a restricted now of gas from the inside to the outside of said conduit; means at the feed end, adapted to feed ore into said heating conduit; means to advance said ore through said conduit from the feed end to the discharge end; means to maintain a predetermined portion of said conduit extending from the feed end toward the discharge end at a predetermined temperature; means to cool a.

predetermined portion of said conduit extending from the discharge end toward the portion provided'with heating means; a stationary receptacle having walls, one of which is provided with an opening which receives the discharge end of the conduit, said receptacle being arranged to receive cooled reduced ore; means to maintain said discharge end and receptacle in a substantially gastight condition and to prevent access of air to said ore in said receptacle; and means at the feed end of said conduit to receive gas generated in said conduit and vented through said orifice means.

6. Apparatus adapted for the reduction of ores comprising an elongated cylindrical heating conduit having a, substantially horizontal straight line axis, a, feed end and a discharge end, said feed end having orifice means providing a restricted flow of gas from the inside to the outside of said conduit while permitting the insertion of a rigid elongated'cleaning tool through said orifice and into said conduit; means at the feed end, adapted to feed ore with 'carbon into said heating conduit; means to advance said ore and carbon through said conduit from the feed end to the discharge end and to agitate said mixture as it advances; means to maintain a predetermined portion of said conduit at a predetermined temperature; means to cool a predetermined portion of said conduit; a receptacle connected to the discharge end of the conduit, to receive cooled ore;- means to maintain said discharge end and receptacle in a substantially gastight condition; and means at the feed end of said conduit to receive gas generated in said conduit and vented through said orifice means.

7. Apparatus adapted for the reduction of ores comprising an elongated cylindrical heating conduit having a straight line axis slightly inclined to a horizontal plane, a, feed end and a discharge end; said feed end having orifice means providing a restricted flow of gas from the inside to the outside ofsaid conduit; conveyor means at the feed end, adapted to feed ore with carbon into said heating conduit; means to rotate said conduiifto advance said ore and carbon through the conduit, to receive reduced ore; means to maintain said discharge end andreceptacle in a substantially gas-tight condition; and means at the feed end of said conduit to receive gas gen. erated in said conduit and vented through said orifice means. y e

8. Apparatus adapted for the reduction of ores comprising a rotatably mounted elongated cylindrical heating conduit having a straight line axis slightly inclined to a horizontal plane, a feed end and a discharge end; said feed end having edge portions defining .a circular opening; conveyor means at the feed end adapted to feed ore into said conduit, said conveyor means having cylindrical walls extending into the space within said conduit and defining with said edge portions a restricted annular orifice of predetermined dimensions; means to rotate said conduit about its axis to advance said ore through said conduit from the feed end to the discharge end; a stationary heating muie surrounding a predetermined portion of said conduit and extending a predetermined distance from the feed end toward the discharge end, said muffle being provided with means to heat said conduit to a predetermined temperature and to maintain that temperature within closely controlled narrow limits; means to cool a predetermined portion of the conduit extending from the discharge end toward the heating muille; a stationary receptacle at the discharge end of the conduit having a circular opening defined by edge portions into which opening the said discharge end protrudes; means providing a substantially gas-tight seal between said conduit and said edge portions; means to withdraw ore from said receptacle While'preventing access of air to said ore in said receptacle and means at the feed end of said conduit to receive and transport to a place of disposal gaseous products evolved in said conduit.

9. Apparatus adapted for the reduction of ores comprising a rotatably mounted elongated cylindrical heating conduit having a straight line axis slightly inclined to a horizontal plane, a feed end and a discharge end; said feed end having edge portions defining a circular opening; conveyor means at the feed end adapted to feed ore into said conduit, said conveyor means having cylindrical walls extending into the space Within said conduit and defining with said edge portions a restricted annular orice of predetermined dimensions; means to rotate said conduit about its axis to advance said ore through said conduit from the feed end to the discharge end; a stationary heating muiiie surrounding a predetermined portion of said conduit and extending a predetermined distance from the feed end toward the-discharge end, said muilie being provided with means to heat said conduit to a predetermined temperature and to maintain that temperature within closely controlled narrow limits; means to cool a predetermined portion of the conduitA extending from the discharge end toward thev heating muflie; a stationary receptacle at the i opening defined by edge portions into which opening the said discharge end protrudes; means providing a substantially gas-tight seal between said conduit and said edge portions; means to withdraw ore from said receptacle while preventing accessy of air to said ore in said receptacle; a hood at the feed end having parts in substantial registry with parts defining the restricted annular orifice at said end, said hood being adapted' to receive gaseous products from said conduit and means to withdraw said gaseous products from said hood and conduct them to a place of disposal.

10. Apparatus of the character described comprising a rotatably mounted elongated heating conduit having a substantially straight line axis slightly inclined to a horizontal plane, a feed .end and a discharge' end; a stationary receptacle at the discharge end having Walls one of which has an opening which receives the discharge end of the conduit, said discharge end being open and in spaced relation to another Wall of said "stationary receptacle; feed means at the feed end to feed a Acharge of solid material into said conduit, said feed means forming with end portions -of the conduit a restricted opening providing a restricted flow of gas from the inside to the out- 4side of the conduit, while permitting insertion through said restricted opening and into said conduit of a rigid cleaning tool; means to prevent access of air into said receptacle while permitting rotation of said conduit and withslightly inclined to a horizontal plane, a feed` end a discharge end; said conduit being open at both the feed end and discharge end; a stationary receptacle at the discharge end of the conduit having a wall provided with an opening which receives said discharge end, said receptacle providing a chamber adapted to receive solid material from the conduit and to permit the removal of said material from said chamber and the rotation of the conduit while excluding access of air to said chamber and conduit; the conduit having an opening at the feed end providing a restricted flow of gas fromthe interior to the exterior of the conduit while permitting the lnsertion through said restricted opening of a rigid cleaning tool.

12. Apparatus of the character described comprising a rotatably mounted elongated heating conduit having a substantially straight line axis slightly inclined to a, horizontal plane, a feed end and a discharge end; receptacle means at the discharge end providing for the discharge of solid material from the conduit into the receptacle,

the removal of said material from the receptacle and the rotation of the conduit while preventing access of air to said receptacle and conduit; and means at the feed end of the conduit constituting a restricted opening and providing a restricted flow of gas from the interior to the exterior of the conduit While permitting insertion of a rigid cleaning tool through said restricted opening and into the interior of the conduit.

.13. In apparatus of the character described including a rotatably mounted elongated heating conduit having a substantially straight line axis slightly inclined to a horizontal plane, a feed end and a discharge end; means at the feed end of the conduit, including a conveyor for feeding solid material into said conduit, providing a restricted opening to restrict the flow of gas from the inside to the outside of said conduit while permitting the insertion through said restricted conduit while permitting discharge of solid material into and removal thereof from said recep-` tacle and means at the feed end of the conduit constituting a restricted opening and providing a restricted ow of gas from the interior to the exterior 0f the conduit while permitting insertion of a rigid cleaning tool through said restricted opening and into the interior of the conduit.

15. Apparatus of the character described, comprising a rotatably mounted elongated heating conduit having substantially straight line axis slightly inclined to a'. horizontal plane, a. feed end and a discharge end, said conduit being open at both-the feed end and discharge end, said conduit having interior surfaces ldefining an empty space providing for the free andl unobstructed passage of solid material therethrough,`recep tacle means at'the discharge end of the conduit to prevent access of air to said conduit while permitting discharge of solid material into and removal thereof from said receptacle, means at the feed end of the conduit, including a conveyor for feeding solid material into said conduit, providing a restricted opening to restrict the flow` of gas from the inside to the outside of said conduit while permitting the insertion through saldrestricted opening and into the interior of said conduit, of a rigid cleaning tool.

ELMER M. WANAMAKER.

ROBERT H. CROMWELL HAROLD L. C i' 

